Earhealth monitoring system and method i

ABSTRACT

Methods of operating an audio device are provided. A method includes calculating estimated sound pressure levels (SPLs) for drive signals directed to an ear canal receiver (ECR) during a time increment Δt; calculating an estimated SPL_Dose during the time increment Δt using the estimated sound pressure levels; and calculating a total SPL_Dose at a time t of the audio device using the estimated SPL_Dose.

This application is a Divisional of U.S. application Ser. No. 11/928,290which is a Continuation-in-Part of U.S. patent application Ser. No.11/757,152 filed on 1 Jun. 2007, the disclosure of which is incorporatedherein by reference in its entirety, which in turn claims priority fromU.S. Provisional Application No. 60/803,708 filed 1 Jun. 2006.

FIELD OF THE INVENTION

The present invention relates to a device that monitors acoustic energydirected to an ear, and more particularly, though not exclusively, to anearpiece that monitors acoustic sound pressure level dose received by auser's ear.

BACKGROUND OF THE INVENTION

With the advent of an industrial society, people are exposed to noisepollution at greater and greater levels; both from background, such asstreet traffic, airplanes, construction sites and intentional exposureto high sound levels such as cell phones, MP3 players, and rockconcerts. Studies show that ear damage, leading to permanent hearingimpairment is not only increasing in the general population, butincreasing at a significantly faster rate in younger populations.

The potential for hearing damage is a function of both the level and theduration of exposure to the sound stimulus. Safe listening durations atvarious loudness levels are known, and can be calculated by averagingaudio output levels over time to yield a time-weighted average. Standarddamage-risk guidelines published by OSHA, NIOSH or other agencies areknown. This calculation can be even further improved by accounting foraspects of the playback scenario, specifically the characteristics ofthe sound source and their proximity to the listener's ear.

Studies have also indicated that hearing damage is a cumulativephenomenon. Although hearing damage due to industrial or backgroundnoise exposure is more thoroughly understood, the risk of exposing one'sself to excessive noise, especially with the use of headphones has alsobeen recently studied. Protecting the ear from ambient noise isprimarily done with the use of static earplugs that attempt to shieldthe inner ear from excessively high decibel noise. Background noisecanceling earphones such as those produced by Bose and others, attemptto protect the ear from excessive ambient noise by producing a counternoise wave to cancel out the ambient noise at the ear. These prior artdevices have been less than satisfactory because they do not completelyprevent high decibel noise from reaching the ear, and do not account forthe duration of exposure to harmful sounds at the ear.

It is also known from the prior art to provide active noise reduction atthe ear to protect the ear from exposure to loud noises as disclosed inU.S. patent Application No. US2005/0254665. The art actively attenuatingnoise reaching the inner ear utilizing a control; a connection with anearpiece and attenuating the noise to the ear. However, there is nomonitoring of the noise over time to account for the cumulative effect.Furthermore, there is no accounting for any restorative effects withinthe ear for sound level exposures which are sufficiently low to allowrecovery, rather than destruction.

Dosimeters, such as that described in U.S. published Application No.US2005/0254667 are known. The device periodically measures prior soundlevel in the ambient environment. However, the device does not take intoaccount the cumulative effect of the noise over multiple incidences ofexposure (e.g., one day to the next) or the effect of any restorativeperiod. Furthermore, no remedial action is automatically taken as aresult of the readings.

It is also known from the prior art that headphones for consumerelectronics have been provided with a predetermined maximum output levelin an attempt to prevent ear damage. This approach is ineffective as itdoes not take into account listening duration and the calculation ofrisk for auditory injury. Other headphones are maximum-limited toproduce levels that can still result in significant overexposure givenenough time, or limit the user to levels, which may not be sufficient toachieve an adequate short term listening level. In the latter case,consumer acceptance for the protective gear could be severely limitedand a product would fail to survive in a competitive market andtherefore be of no use.

Another alternative known in the art is to reduce the headphone outputlevels by increasing earphone impedance via an accessory placed betweenthe media player and the earphones. The limitation of this approach isthat it gives no consideration to the duration of exposure, and againeither the user's chosen listening level cannot be achieved because themaximum level is too limited, or the level is sufficient to allow theuser access to high enough sound levels, but risk overexposure due topotential duration of use.

It is known from U.S. Publication No. 2007/0129828 to provide automatedcontrol of audio volume parameters in order to protect hearing. A methodof operating a media player includes the step of playing back audiomedia and refining a maximum volume parameter for the playing of themedia by the media player. The refining is based at least in part on theplayback of audio media during a time period existing prior to theexecution of refining the maximum volume allowed. The refinement isintended to minimize harm to the user's hearing.

Applicants cannot confirm that such an approach has been commercialized.However, even if commercialized, it suffers from the shortcomings thatthe refinement is based on a theoretical noise volume delivered to theear as a function of the output signal of the device and parameters ofthe earpiece connected to the device and is based upon a credit systembased on volume. There is no measurement of the actual noise deliveredto the ear. Furthermore, the calculation does not take into account theambient noise of the device user nor the noise reduction rate of theearpiece relative to the ambient noise. In other words, the actualvolume level to which the ear is exposed is not taken into account.Accordingly, a severe miscalculation of the actual ear exposure, andresulting ear harm, may exist as a result of use of this related artmethod. Additionally the credit system is not described in detailsufficient for one of ordinary skill to construct the device. Forexample U.S. Publication No. 2007/0129828 refers to Cal-OSHA profiles,and states in the same paragraph that Cal-OSHA appear to be rudimentaryand does not deal with exposure “in a sophisticated way with varyingexposure over time” and does not “ . . . account for recovery.” However,U.S. Publication No. 2007/0129828 states in one example “ . . . themaximum allowed volume is determined based upon determined credits withreference to a profile such as profiles provided by . . . (Cal-OSHA) . .. ” However, U.S. Publication No. 2007/0129828, stated that Cal-OSHAdoesn't take into effect recovery, and additionally fails to refer toany detailed recovery calculation. Additionally, the credit system isbased upon volume, rather than a predicted sound pressure level (PSPL)emitted by a speaker, and thus is an inaccurate predictor of soundpressure level (SPL) experienced by a user's ears due to emissions fromthe speaker.

Accordingly, a system that overcomes the shortcomings in the related artwould be useful.

BRIEF SUMMARY OF THE INVENTION

At least one exemplary embodiment is directed to a method of operatingan audio device comprising: calculating estimated sound pressure levelsfor drive signals directed to an ear canal receiver (ECR) (which canresult in an emitted acoustic signal by the ECR) during a time incrementΔt; calculating an estimated SPL_Dose during the time increment Δt usingthe estimated sound pressure levels; and calculating a total SPL_Dose atthe time t of the audio device using the estimated SPL_Dose. Additionalexemplary embodiments include comparing the estimated sound pressurelevels to a permissible sound level (PSL), and if the estimated soundpressure levels are less than PSL within an error margin, then the stepof calculating an estimated SPL_Dose uses a recovery function tocalculate the updated estimated SPL_Dose during the time increment Δt.

Additional exemplary embodiments can include: calculating estimatedsound pressure levels (SPL1) for drive signals directed to an ear canalreceiver (ECR) during a time increment Δt, when the ECR is in the ECRmode; measuring sound pressure levels (SPL2) for ambient acousticsignals received by the ECR during the time increment Δt, when the ECRis in the ear canal microphone (ECM) mode; calculating an estimatedSPL_Dose during the time increment Δt using at least one of SPL1 andSPL2; calculating a total SPL_Dose of the audio device at the time tusing the estimated SPL_Dose; and comparing either sound pressure levelsSPL1 or SPL2 to a permissible sound level (PSL), and if the used soundpressure levels, SPL1 or SPL2, is less than PSL within an error margin,then the step of calculating an estimated SPL_Dose uses a recoveryfunction to calculate the updated estimated SPL_Dose during the timeincrement Δt.

At least one further exemplary embodiment is directed to a method ofoperating an audio device comprising: calculating estimated soundpressure levels (SPL1) for drive signals directed to an ear canalreceiver (ECR) during a time increment Δt, when the ECR is in the ECRmode; predicting a sound pressure level (PSPL1) for ambient acousticsignals that would be received by the ECR during the time increment Δt,if the ECR was in the ECM mode but is in ECR mode; calculating anestimated SPL_Dose during the time increment Δt using SPL1 and PSPL1;and calculating a total SPL_Dose of the audio device at time t using theestimated SPL_Dose.

At least one exemplary embodiment is directed to a method of operatingan audio device comprising: calculating estimated sound pressure levelsfor drive signals directed to an ear canal receiver (ECR) during a timeincrement Δt; calculating an estimated SPL_Dose during the timeincrement Δt using the estimated sound pressure levels; comparing theestimated sound pressure levels to a permissible sound level (PSL), andif the estimated sound pressure levels are less than PSL then the stepof calculating an estimated SPL_Dose uses a recovery function that is atleast one of a linear function and an exponential function to calculatethe estimated SPL_Dose during the time increment Δt; and calculating atotal SPL_Dose of the audio device at the time “t” using the estimatedSPL_Dose, where t=t₀+Δt, where t₀ is the time at the beginning of thetime increment Δt.

At least one exemplary embodiment is directed to a method of operatingan audio device comprising: calculating estimated sound pressure levels(SPL1) for drive signals directed to an ear canal receiver (ECR) duringa time increment Δt, when the ECR is in the ECR mode; measuring soundpressure levels (SPL2) for ambient acoustic signals received by the ECRduring the time increment Δt, when the ECR is in the ECM mode;predicting a sound pressure level (PSPL1) for ambient acoustic signalsthat would be received by the ECR during the time increment Δt, if theECR was in the ECM mode but is in the ECR mode; calculating an SPL totalduring the time increment Δt using SPL1 and PSPL1 when the ECR is in theECR mode. If the ECR is in the ECM mode during the time increment Δtthen SPL total during the time increment Δt is calculated using SPL2;calculating an estimated SPL_Dose during the time increment Δt usingSPL1 and PSPL1 when the ECR is in ECR mode and SPL2 when ECR is in ECMmode; comparing the SPL total to a permissible sound level (PSL), and ifSPL total is less than PSL then the step of calculating an updatedestimated SPL_Dose uses a recovery function that is at least one of alinear function and an exponential function to calculate the estimatedSPL_Dose during the time increment Δt; and calculating a total SPL_Doseof the audio device at time t using the estimated SPL_Dose, wheret=t₀+Δt, where t₀ is the time at the beginning of the time increment Δt.

Further areas of applicability of exemplary embodiments of the presentinvention will become apparent from the detailed description providedhereinafter. It should be understood that the detailed description andspecific examples, while indicating exemplary embodiments of theinvention, are intended for purposes of illustration only and are notintended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the system for measuring and determiningexposure to sound over time at the ear constructed in accordance with afirst exemplary embodiment of the invention.

FIG. 2 is a block diagram of the system in accordance with at least oneexemplary embodiment of the invention in situ in the ear;

FIG. 3 is a flow chart for calculating listening fatigue in accordancewith at least one embodiment of the invention by measuring a quantity(e.g., the sound pressure level) over time as perceived at the ear;

FIG. 4 is a flow chart for determining a weighted ear canal soundpressure level in accordance with another exemplary embodiment of theinvention;

FIG. 5 is a flow chart for determining a personalized recovery timeconstant in accordance with another exemplary embodiment of theinvention;

FIG. 6 is a flow chart for determining an update epoch in accordancewith at least one exemplary embodiment of the invention;

FIG. 7 is a flow chart for determining an update epoch in accordancewith yet another exemplary embodiment of the invention;

FIG. 8 illustrates the general configuration and terminology inaccordance with descriptions of exemplary embodiments;

FIGS. 9A-9C illustrates an example of a temporal acoustic signal and itsconversion into a spectral acoustic signature;

FIG. 10 illustrates a generalized version of an earpiece and someassociated parts in an ear canal;

FIG. 11 illustrates an earpiece according to at least one exemplaryembodiment;

FIG. 12 illustrates a self contained version of an earpiece according toat least one exemplary embodiment;

FIG. 13 illustrates an earpiece where parts are not contained in theearpiece directly according to at least one exemplary embodiment;

FIG. 14A illustrates a general configuration of some elements of anearpiece according to at least one exemplary embodiment;

FIG. 14B illustrates a flow diagram of a method for SPL Dose calculationaccording to at least one exemplary embodiment;

FIG. 14C illustrates a flow diagram of a method of SPL Dose calculationaccording to at least one exemplary embodiment;

FIG. 14D illustrates a flow diagram of a method of SPL Dose calculationaccording to at least one exemplary embodiment;

FIGS. 15A-15E illustrate a method of switching between ECR and ECM modesin accordance with at least one exemplary embodiment;

FIGS. 16A-16C illustrate the formation of SPL total from ECM and ECRvalues and estimated values (PSPL);

FIGS. 17A-17D illustrate the formulation of an SPL-Dose by anon-limiting example of an optional end of day correction to theprevious estimated values (PSPL);

FIGS. 18A to 18N illustrate various non-limiting examples of earpiecesthat can use methods according to at least one exemplary embodiment;

FIG. 19 illustrates a line diagram of an earpiece (e.g., earbud) thatcan use methods according to at least one exemplary embodiment; and

FIG. 20 illustrates the earpiece of FIG. 19 fitted in an ear.

DETAILED DESCRIPTION OF THE INVENTION

The following description of at least one exemplary embodiment is merelyillustrative in nature and is in no way intended to limit the invention,its application, or uses.

Processes, techniques, apparatus, and materials as known by one ofordinary skill in the relevant art may not be discussed in detail butare intended to be part of the enabling description where appropriate,for example the fabrication and use of transducers. Additionally in atleast one exemplary embodiment the sampling rate of the transducers canbe varied to pick up pulses of sound, for example less than 50milliseconds.

In all of the examples illustrated and discussed herein, any specificvalues, for example the sound pressure level change, should beinterpreted to be illustrative only and non-limiting. Thus, otherexamples of the exemplary embodiments could have different values.

Note that similar reference numerals and letters refer to similar itemsin the following figures, and thus once an item is defined in onefigure, it may not be discussed for following figures.

Note that herein when referring to correcting or preventing an error ordamage (e.g., hearing damage), a reduction of the damage or error and/ora correction of the damage or error are intended.

At least one exemplary embodiment of the invention is directed tomeasuring and determining the exposure of sound to the ear over time.Reference is made to FIG. 1 in which a system, generally indicated as100, is constructed in accordance with at least one exemplary embodimentof the invention. System 100 includes an audio input device 113 forreceiving sound at the ear. As will be discussed below, audio inputdevice 113 can include an analog audio input 11, 23 and a digital audioinput 19. In at least one exemplary embodiment, audio input device 113receives audio input from at least one of three sources, namely; ambientnoise around the ear, direct input noise such as a MP3 player or otherdevice which can produce a digital audio input at digital audio input19, and noise as detected within the ear canal 31 (FIG. 2). The audioinput device 113 outputs an audio signal corresponding to the receivedsound. Analog output signals from analog audio inputs 11, 23 areconverted to a digital signal by an analog-to-digital (A/D) converter118 so that digital sound signals are input into an input level detector120.

Input level detector 120 determines the sound pressure level of thesound received at audio input device 113. Input level detector 120outputs a sound pressure level (SPL) signal, which is input to aminimum-level threshold detector 122. Minimum level threshold detector122 determines whether or not the sound pressure level as detected byinput level detector 120 exceeds a minimum level threshold. As will bediscussed below, the minimum level threshold can be the PSL (e.g.,effective quiet level) of the individual, or some predetermined levelsubstantially corresponding to a level which is ear damage neutral overtime or a level of interest, such as 80 dB, because of its effect on theear. Therefore, if the minimum level threshold is detected as beingexceeded, a signal indicating a sound pressure level in excess of theminimum level threshold is output to a start timer 124, which triggers adigital timer system 126 to begin a clock. Conversely, if the inputsound pressure level is detected as being below the minimum threshold, asignal indicating the sound pressure level is below the minimum levelthreshold is output to a start timer 124, which triggers a digital timersystem 126 to begin a clock of a restorative period. If the soundpressure level is at the minimum threshold (within a margin of error),no clock needs to be started because this is neutral to the desiredeffect. In a preferred embodiment, the clock signal is changed withevery significant (more than 1 dB by way of example) change in soundpressure level to get an accurate profile of sound exposure over time.

Once the sound pressure level as detected at input level detector 120decreases to or is below the minimum threshold level, a stop timersignal is output from stop timer 128 to digital timer system 126 to stopthe clock corresponding to exposure to the excessively intense level.Digital timer system 126 outputs a clock value corresponding to the timeperiod at which the minimum level threshold was not met, or in thepreferred embodiment, for each period corresponding to a discrete levelchange.

A data memory or learning history database 127 receives the clock valuefrom digital timer system 126 as well as the actual input level detectedat input level detector 120 and determines a listening history or soundpressure level exposure history. The sound pressure level exposurehistory is a record of the user's exposure to sound pressure levels overtime. Because the effect of exposure is cumulative, it is important thatthe exposure history be maintained. The listening history, as will bediscussed below, can include real ear level data, listening durationdata, time between listening sessions, absolute time, sound pressurelevel dose (SPL Dose) data, including any restorative sound level,number of acoustic transients and crest factor and other data.

The sound pressure level exposure history or listening history includesboth the listening habits history and the environmental or ambient noiseexposure history. The environmental noise exposure history is theexposure of a user to environmental noise over time as a result of theauditory stimuli inherent to the environment where the user is present.This can be highway traffic, construction site, even the restorativeeffect of the quiet sound pressure levels, e.g., those typicallyencountered in a library whereas, the listening habits history isassociated for the purposes for this disclosure with user-directedauditory stimuli such as music, words, other noises, which a userintentionally encounters for a purpose such as communication, learning,and enjoyment. Therefore, database 127, as will be discussed below,stores the cumulative SPL exposure.

It should be noted that in at least one exemplary embodiment, minimumlevel threshold detector 122 also starts the timer 124 when the soundpressure level is below the predetermined level. In this way, therestorative effect of below PSL (e.g., effective quiet noise) isaccumulated for determining overall exposure damage potential.

In effect, the only time that digital timer system 126 is not running iswhen the detected sound pressure level signal is at the minimum levelthreshold. A listening fatigue calculator 130 receives the input levelsignal from input level detector 120 and data from the data memorylistening history 127, and determines whether or not listening fatigueor hearing damage is likely to occur as a result of further exposure.Hearing damage is the injury to the hearing mechanism includingconductive and sensorineural decrement in hearing threshold levels. Itcan be either temporary or permanent so long as it is a result of thenoise exposure is above PSL (e.g., Effective Quiet). In other words,listening fatigue calculator 130 will output a signal when a thresholdsound exposure, determined as a function of exposure time and soundpressure level, as will be discussed in greater detail below, isachieved. At that point, a listening fatigue signal is output.

It should be noted that in an alternative embodiment, system 100 canmake use of an ambient noise detection/cancellation system 142 as knownin the art. These systems produce signals, which cancel sound pressurelevels at certain frequencies and/or certain levels to reduce the effectof undesired noise, whether environmental noise or user directed noise.It will have some effect in elongating the permissible exposure time bynegating the sound pressure level detected by input level detector 120.

In at least one exemplary embodiment, the signal from the listeningfatigue calculator is utilized to prevent damage and encourages someaction by the user when exposure levels are near damaging levels.Therefore, in one non-limiting example, a listening fatigue display 140is provided for receiving the signal from the listening fatiguecalculator and displaying to the user a prompt to discontinue exposureto the sound level from the damaging sound source or audio source.

In another non-limiting example, the signal from the listening fatiguecalculator is output to an audio warning source 132, which outputs anoutput audio warning to the user notifying the user that exposure to thesound source has reached critical levels.

In at least one exemplary, but non-limiting, embodiment, as will bediscussed below, system 100 includes an output acoustical transducer 25to provide an audio signal to the ear. Output acoustical transducer 25operates under the control of a digital signal processor (DSP) 134.Digital signal processor 134 receives a digital audio signal from inputlevel detector 120, which acts as a pass through for the digitizedsignals from audio input device 113. Digital signal processor 134 passesthe sound signals through to a digital to analog (D/A) converter 136 todrive acoustical transducers 25 to recreate the sound received at audioinput device 113 inside the ear canal 31 in at least one exemplaryembodiment of the invention as shown in FIG. 2. With such an exemplaryembodiment, audio warning source 132 provides an output to digital soundprocessor 134 causing output acoustical transducer 25 to output awarning sound inside the ear of the user.

Additionally, in at least one further exemplary embodiment, listeningfatigue calculator 130 outputs a listening fatigue signal to digitalprocessor 134 which causes digital signal processor 134 to attenuate thesound signal prior to output to acoustical transducer 25 to reduce thesignal output level by any of the linear gain reduction, dynamic rangereduction, a combination of both, or a complete shutdown of transducer25. Attenuation would be at least to the level, if not below, the PSL(e.g., effective quiet level) to allow for ear recovery prior to damage.

It should be noted, that because personal hearing threshold anddiscomfort levels can change from person to person, and because both ofthe time intervals are a function of many variables, in a non-limitingexample, to provide a dynamic ever-changing response, system 100operates under software control. The configuration of the digital soundprocessor 134, listening fatigue calculator 130, the minimum levelthreshold detector 122, and the input level detector 120 are operatedunder software control.

In an exemplary embodiment of the invention, the control programs arestored in a program memory 148 for operating the firmware/hardwareidentified above. Furthermore, the program stored within memory 148 canbe personalized as a result of testing of the user's ear, or by othermodeling methods, in which system 100 includes a software interface 144for receiving online or remote source updates and configurations. Thesoftware interface 144 communicates with a data port interface 146within system 100, which allows the input of software updates to programmemory 148. The updates can be transmitted across a distributedcommunications network, such as the Internet, where the updates take theform of online updates and configurations 143.

It should be noted that there is multiple functionality distributedacross system 100. In at least one exemplary embodiment, at least audioinput device 113 and acoustical transducer 25 are formed as an earpiece,which extends into the outer ear canal so that the processing of signalspertains to sound received at the ear. However, it is well within thescope of at least one exemplary embodiment of the invention to providesubstantially all of the functionality in an earpiece so that system 100is a “smart device.”

Also note that when referring to measurements in decibels (dB), one isreferring to a logarithmic ratio. For example dB is defined as:

$\begin{matrix}{{S\; P\; L} = {{\beta ({dB})} = {{10\log \frac{I}{I_{0}}} = {10\log \frac{\Delta \; P^{2}}{\Delta \; P_{0}^{2}}}}}} & (1)\end{matrix}$

Where I is the intensity measured, I₀ is a reference intensity, I₀=10⁻¹²W/m², and P₀ is a reference pressure, ΔP₀=20 micropascals, and whereΔP is the root mean squared pressure amplitude in a measured pressurewave (e.g., using a transducer). Thus, the sound pressure level (SPL)can be measured in dB.

Alternatively one can use the above equation and solve for measuredpressures instead. For example:

ΔP(t)=10^((SPL(t)/20.0)) ΔP ₀  (2)

In the discussion of formulas herein we refer to SPL as a non-limitingexample and one of ordinary skill in the arts could re-derive theequations in terms of measured pressures, ΔP, both are intended to liewithin the scope of at least one exemplary embodiment. Reference is nowmade to FIG. 2 in which system 100 in which the transducerconfiguration, that portion of system 100, which converts sound pressurelevel variations into electrical voltages or vice versa is shown. Inthis embodiment, acoustic transducers include microphones as an inputand loudspeakers as an acoustical output.

FIG. 2 depicts the electro acoustical assembly 13 (also referred toherein as an in-the-ear acoustic assembly 13 or earpiece 13), as itwould typically be placed in the ear canal 31 of ear 17 of user 35. Theassembly is designed to be inserted into the user's ear canal 31, and toform an acoustic seal with the walls 29 of the ear canal 31 at alocation 27, between the entrance 15 to the ear canal 31 and thetympanic membrane or eardrum 33. Such a seal is typically achieved bymeans of a soft and compliant housing of assembly 13. A seal is criticalto the performance of the system in that it creates a closed cavity inear canal 31 of approximately 0.5 cc in a non-limiting example betweenthe in-ear assembly 13 and the ear's tympanic membrane 33.

As a result of this seal, the output transducer (speaker) 25 is able togenerate a full range bass response when reproducing sounds for thesystem user. This seal also serves to significantly reduce the soundpressure level at the user's eardrum 33 resulting from the sound fieldat the entrance 15 to the ear canal 31. This seal is also the basis forthe sound isolating performance of the electroacoustic assembly 13.Located adjacent to speaker 25, is an ear canal microphone (ECM) 23,which is also acoustically coupled to closed cavity 31. One of itsfunctions is that of measuring the sound pressure level in cavity 31 asa part of testing the hearing sensitivity of the user as well asconfirming the integrity of the acoustic seal and the working conditionof itself and speaker 25. Audio input 11 (also referred to herein asambient sound microphone (ASM) 11) is housed in assembly 13 and monitorssound pressure at the entrance 15 to the occluded ear canal. Thetransducers can receive or transmit audio signals to an ASIC 21 thatundertakes at least a portion of the audio signal processing describedabove and provides a transceiver for audio via the wired or wirelesscommunication path 119.

In the above description the operation of system 100 is driven by soundpressure level, i.e. sound levels are monitored for time periods orepochs during which the sound pressure level does not equal the minimumlevel threshold or is constant. However, as will be discussed inconnection with the next exemplary embodiments of the invention, system100 can also operate utilizing fixed or variable sampling epochsdetermined as a function of one or more of time and changes in soundpressure level, sound pressure dosage level, weighting functions to thesound pressure level, and restorative properties of the ear.

Reference is now made to FIG. 3 in which a flow chart for monitoring thesound pressure level dose at various sample times n is provided. Theprocess is started in a step 302. An input audio signal is generated ina step 304 at either the ear canal microphone (ECM) 23 or the ambientsound microphone (ASM) 11. Changes in SPL_Dose resulting from durationof exposure time is a function of the sound pressure level, therefore,the epoch or time period used to measure ear exposure or, moreimportantly, the time-period for sampling sound pressure level isdetermined in a step 305. The update epoch is used in the SPL Dosefunction determination as well as to effect the integration period forthe sound pressure level calculation that, as will be discussed below,is used to calculate the weighted ear canal sound pressure level.

Reference is now made to FIGS. 6 and 7. In FIG. 6, a method is definedto change the update epoch as a function of the weighted ear canal soundpressure level, which will be discussed in greater detail below. System100 is capable of determining when earpiece 13 is in a charger orcommunication cradle (i.e., not in use in the ear of the user). In astep 684, a predetermined standard is provided for the update epoch, 60seconds in this example. In step 688, the update epoch is set as thein-cradle update epoch. The in-cradle state is detected in step 686. Ifit is determined in a step 690 that earpiece 13 (also referred to hereinas earphone device 13) is in a charger or cradle mode, then the updateepoch is set as the in-cradle epoch; in the step 688.

However, if in step 690 it is determined that the earphone device 13 isin use, in other words “not in the cradle”, then, by default, an audiosignal is input to earpiece 13 in step 692. In step 693, an ear canalsound pressure level is estimated as a function of the audio input atstep 692. The current (n) ear canal sound pressure level estimate isstored as a delay level in a step 698. An audio input is determined at alater time when step 692 is repeated so that a second in-time ear canalsound pressure level estimate is determined.

In a step 600, the delayed (n−1) or previous sound pressure level iscompared with the current (n) ear canal sound pressure level estimate tocalculate a rate of change of the sound pressure level. The change levelis calculated in units of dB per second. This process of step 692through 600 is periodically repeated.

In a step 606, it is determined whether or not the sound pressure levelchange is less than a predetermined amount (substantially 1 dB by way ofnon-limiting example) between iterations, i.e., since the last time theear canal sound pressure level is calculated. If the change is less thanthe predetermined amount, then in step 604 the update epoch isincreased. It is then determined in a step 602 whether or not the epochupdate is greater than a predefined amount D set in step 694 as amaximum update epoch such as 60 seconds in a non-limiting example. If infact, the update epoch has a value greater than the maximum update epochD then the update epoch is set at the higher value D in step 608.

If it is determined in step 606 that the sound pressure level change is,in a non-limiting example, greater than −1 dB, but less than +1 dB asdetermined in step 612, then the update epoch value is maintained in astep 610. However, if it is determined that the sound pressure levelchange is, in a non-limiting example, greater than +1 dB, then theupdate epoch value is decreased in a step 618 to obtain more frequentsampling. A minimum predetermined update epoch value such as 250microseconds is set in a step 614. If the decreased update epochdetermined in step 618 is less than, in other words an even smallerminimum time-period than the predetermined minimum update epoch E, thenthe new update epoch is set as the new minimum update epoch value insteps 616 and 622. In this way, the sample period is continuously beingadjusted as a function of the change in sound pressure level at the ear.As a result, if the noise is of a transient variety as opposed to aconstant value, the sampling interval will be changed to detect suchtransients (e.g., spikes) and can protect the ear.

Reference is now made to FIG. 7 in which a method for changing theupdate epoch is illustrated as a function of the way that the ear canalsound pressure level estimate is provided. Again, in accordance with atleast one exemplary embodiment of the invention, the update epoch isdecreased when the ear canal sound pressure level is high or increasing.

The difference between the embodiment of FIG. 7 and the embodiment ofFIG. 6 is that the update epoch is not continuously adjusted, but ismore static. If the ear canal sound pressure level is less than PSL(e.g., effective quiet, a decibel level which when the ear is exposed toover time does not damage or restore the ear), then the update epoch isfixed at a predefined maximum epoch value and this is the value used bysystem 100 as will be discussed in connection with FIG. 3 below. In thisembodiment, if the ear canal sound pressure level is determined to begreater than a permissible (or permitted) sound level (PSL) (e.g.,effective quiet), then the update epoch is fixed at a shorter minimumvalue and this is returned as the update epoch to be utilized.

In FIG. 7, specifically, as with FIG. 6, an in-cradle update epoch of 5seconds by way of non-limiting example, is stored in system 100 in astep 784. In a step 788, the initial update epoch is set as thein-cradle update epoch. A maximum update epoch time, such as 2 secondsby way of non-limiting example, is stored in a step 794. In a step 714,an initial minimum update epoch (250 microseconds in this non-limitingexample) is stored.

In a step 786 and step 790 it is determined whether or not system 100 isin a non-use state, i.e., being charged or in a cradle. If so, then theupdate epoch is set at the in-cradle update epoch. If not, then adigital audio signal is input from ear canal microphone 23 in step 792.A sound pressure level is estimated in step 795. It is then determinedwhether or not the ear canal sound pressure level is less than PSL(e.g., effective quiet) in a step 732. If the sound pressure level isless than the PSL (e.g., effective quiet) as determined in step 732,then the update epoch is set at the maximum update epoch in a step 730.If the sound pressure level is louder than the effective quiet, then instep 716, the update epoch is set to the minimum update epoch.

Returning to FIG. 3, in a non-limiting exemplary embodiment, the updateepoch is set at 10 seconds in a step 302 utilizing either a constantpredetermined sample time, or either of the methodologies discussedabove in connection with FIGS. 6 and 7. In a step 306, the input audiosignal is sampled, held, and integrated over the duration of the epochas determined in step 308. As a result, the update epoch affects theintegration period utilized to calculate the sound pressure level doseas a function of the sound pressure level and/or as the weighted earcanal sound pressure level.

In a step 310, an earplug noise reduction rating (NRR) is stored. Thenoise reduction rating corresponds to the attenuation effect of earpiece13, or system 100, on sound as it is received at audio input 11 andoutput at the output transducer 25 or as it passes from the outer ear tothe inner ear, if any exemplary embodiment has no ambient soundmicrophone 11. In a step 311, a weighted ear canal sound pressure levelis determined, partially as a function of the earplug noise reductionrating value.

Reference is now made to FIG. 4 where a method for determining theweighted ear canal sound pressure level in accordance with at least oneexemplary embodiment of the invention is illustrated. Like numerals areutilized to indicate like structure for ease of discussion andunderstanding. Weighting is done to compensate for the manner in whichsound is perceived by the ear as a function of frequency and pressurelevel. As sounds increase in intensity, the ear perceived loudness oflower frequencies increases in a nonlinear fashion. By weighting, if thelevel of the sound of the field is low, the methodology and systemutilized by at least one exemplary embodiment of the invention reducesthe low frequency and high frequency sounds to better replicate thesound as perceived by the ear.

Specifically, a weighting curve lookup table, such as A-weighting, actsas a virtual band-pass filter for frequencies at sound pressure levels.In a step 304, the audio signal is input. In step 410,frequency-dependent earplug noise reduction ratings are stored. Thesevalues are frequency-dependent and in most cases, set asmanufacturer-specific characteristics.

As discussed above, in a step 306, the input audio signal is shaped,buffered and integrated over the duration of each epoch. The soundpressure level of the shaped signal is then determined in a step 436. Itis determined whether or not ambient sound microphone (ASM) 11 wasutilized to determine the sound pressure level in a step 444. Ifmicrophone 11 was utilized, then the frequency-dependent earplug noisereduction rating of earpiece 13 must be accounted for to determine thesound level within the ear. Therefore, the noise reduction rating, asstored in step 310, is utilized with the sound pressure level todetermine a true sound pressure level (at step 446) as follows:

SPL_(ACT)=SPL−NRR:  (3)

where sound pressure SPL_(ACT) is the actual sound pressure levelreceived at the ear medial to the ECR, SPL is the sound pressure leveldetermined in step 436 and NRR is the noise reduction rating valuestored in step 410.

If the ambient sound microphone (ASM) 11 is not used to determine thesound pressure level then the sound pressure level determined in step436 is the actual sound pressure level. So that:

SPL_(ACT)=SPL  (4)

It is well within the scope of at least one exemplary embodiment of theinvention to utilize the actual sound pressure level as determined sofar to determine the affect of the sound pressure level received at theear on the health of the ear. However, in at least one exemplaryembodiment, the sound pressure level is weighted to better emulate thesound as received at the ear. Therefore, in a step 412, a weightingcurve lookup table is stored within system 100. In a step 440, theweighting curve is determined as a function of the actual sound pressurelevel as calculated or determined above in steps 436, 446 utilizing aweighting curve lookup table such as the A-weighting curve. TheA-weighting curve is then applied as a filter in step 438 to the actualsound pressure level. A weighted sound pressure level valuerepresentative of a sampled time period (SPL_W(n)) is obtained to beutilized in a step 414.

The weighting curve can be determined in step 440 by applying afrequency domain multiplication of the sound pressure level vector andthe weighting curve stored in step 412. In this exemplary embodiment theweighting curve would be appropriate for direct multiplication with theSPL in the frequency domain (i.e., SPL(f)). In another exemplaryembodiment the weighted SPL can be expressed as a weighting of themeasured pressure vector as:

$\begin{matrix}{{{SPL\_ W}\; (n)(t)} = {20{\log( \frac{\Delta \; P^{W_{A}}}{\Delta \; P_{0}} )}}} & (5)\end{matrix}$

where ΔP(t) is the measured temporal change in root mean squaredpressure, which can be converted into spectral space (e.g., FFT) asΔP(f) which is the measured spectral change in pressure, which can inturn be multiplied by a weighting function (e.g., A-weighting),W_(A)(f)) and expressed as ΔP^(W) ^(A) (f)=ΔP(f)·W_(A)(f)−, and thenreconverted (e.g., inverse FFT) into temporal space to obtain ΔP^(W)^(A) (t). To obtain a single value various integration or summation overthe n-th time interval (e.g., which can change in time) can beperformed. For example:

$\begin{matrix}{{{SPL\_ W}\; (n)} = {\frac{1}{\Delta \; t_{n}}{\int_{t_{n - 1}}^{t_{n}}{10{\log( \frac{( {\Delta \; {P^{W_{A}}(t)}} )^{2}}{\Delta \; P_{0}^{2}} )}\ {t}}}}} & (6)\end{matrix}$

The time during which a user may be exposed to the sound levelSPL_W(n),i.e. the time to 100% allowable dosage at SPL level SPL_W(n),is referred to below as Time_(—)100% (n).

The weighting curves can be stored as a lookup table on computer memory,or can be calculated algorithmically. Alternatively, the input audiosignal can be filtered with a time or frequency domain filter utilizingthe weighting curve stored in step 412 and the sound pressure level ascalculated. For low-level sound pressure levels, those less than 50 dB,by way of non-limiting example, a weighting curve, which attenuates lowand high frequencies can be applied (similar to an A-weighting curve).For higher sound pressure levels, such as more than 80 dB, by way ofnon-limiting example, the weighting curve can be substantially flat or aC-weighting curve. The resulting weighted ear canal sound pressure levelduring any respective sampling epoch is returned as the system outputSPL_W(n) in step 414. Note that herein various conventional weightingschemes are discussed (e.g., A-weighting, C-weighting) however in atleast one exemplary embodiment non-conventional weighting schemes can beused. For example, generally the threshold level of hearing sensitivity(threshold of detection) is referenced in dB, where 20 micropascals istypically used as the minimum threshold level of pressure variation thatan average person can detect. This reference value tends to be used atall frequencies, although the threshold level varies with frequency.Thus, one weighting scheme is to adjust the reference 0 dB level on afrequency basis, by using a conventional dB of threshold hearing chart,which provides the dB (f) at threshold level. A weighting function canbe used where the value is about 1 at the reference value (e.g.,equivalent to 20 micropascals) at a reference frequency (e.g., 1000 Hz).The other values (e.g., as a function of frequency) of the weightingfunction can vary depending upon the reference threshold pressurevariation for the particular frequency, for example if at 30 Hz thethreshold level in dB is 65 dB, then the weighting value can be 1/65 at30 Hz, de-emphasizing the loudness and/or intensity at 65 dB when SPLDose (f) is calculated.

Returning to FIG. 3, a safe listening time is calculated by comparingthe weighted sound pressure level with the PSL (e.g., effective quietlevel) in step 316. Therefore, a value A corresponding to how far fromsafe listening the sound pressure level is, is determined by theequation:

A=SPL_(—) W(n)−PSL  (7)

where PSL is the permissible sound level, for example PSL=EfQ, where EfQis equal to the sound level of effective quiet (as stored at step 312).However PSL can be any level chosen for the particular circumstance, forexample lower than EfQ.

By utilizing this simple comparative function, fewer machinations andprocesses are needed. System 100 takes advantage of the fact thatbecause the PSL (e.g., effective quiet level) can be neutral to the ear,sound pressure levels significantly above the PSL (e.g., effective quietlevel) are generally damaging and noise levels below the PSL (e.g.,effective quiet) generally allow for restoration/recovery.

In a step 318, the remaining safe listening time at the beginning of anycurrent sampling epoch can be calculated by Time_(—)100% minus the timeduration of exposure up to the current sampling epoch. Note that anegative number can occur, indicating that no safe listening timeremains. The estimated time (e.g., in hours) until the individual'ssound exposure is such that permanent threshold shift may occur,ignoring any previous sound exposure and assuming that the SPL of thesound field exposed to the individual remains at a constant level L canbe calculated as follows:

Time_(—)100%(n)=T _(c)/(2̂((SPL_(—) W(n)−PSL)/ER));  (8)

Where PSL is the permissible sound level, and Tc is the critical timeperiod. For example, if Tc (Critical Time) is 8 hours and PSL is 90 dBA,then that accepts that ˜22-29% of people are at risk for hearing loss.If Tc is 8 hours and PSL is 85 dBA, then that accepts that ˜7-15% ofpeople are at risk, likewise for if Tc is 24 hours and PSL is 80 dBA,same 7-15% at risk. Thus Time_(—)100% (n) reflects a reduction of therisk to a chosen level. Note that T_(c) is the critical time period ofexposure that one is looking at (e.g., 8 hours, 24 hours), and ER is theexchange rate, for example can be expressed as:

Time_(—)100%(n)=8(hours)/(2̂((SPL_(—) W(n)−85dBA)/3dB))  (9)

These values assume a recovery period of 16 hours at a SPL level duringthat time of less than 75 dBA (where dBA refers to Decibels of anA-weighted value). Of course the realism of such an assumption isquestionable given music, TV, and other listening habits of individuals.Thus, we are concerned with exposure over a 24 hour period. Thus,Time_(—)100% (n) can be expressed for a 24 hour period (e.g.,T_(c)=24(hours)), where, for example using an equal energy assumption(i.e., ER of 3 dBA), as:

Time_(—)100%(n)=24/(2̂((SPL_(—) W(n)−PSL)/3)).  (10)

Another further example is the situation where PSL=EfQ, where theEffective Quiet, EfQ is defined as the highest sound level that does notcause temporary or permanent hearing threshold shift, nor does it impederecovery from temporary hearing threshold shift. For broadband noise, itcan be 76-78 dBA, although these numbers can be different or refinedover time based upon research and/or measurement history.

As a non-limiting example, the lower bound of SPL_W(n) dictating theTime_(—)100% equation would be SPL_W(n)=PSL, and the upper bound of theSPL_W(n) dictating Time_(—)100% equation would be about SPL_W(n)=115 dB.

Note that in at least one exemplary embodiment, the acoustic signalsmeasured by an ECM or an ECR in ECM mode, can be used to detect a user'svoice, for example using the technology discussed in Webster et al.,U.S. Pat. No. 5,430,826, incorporated by reference in its entirety. Ifvoice is detected then by the magnitude of the SPL (e.g., 80 dB) one cantell whether the user is speaking as compared to a non-user's voice(e.g., 50 dB) that has been attenuated by the earpiece. When a user'svoice is detected then SPL_W(n) can be reduced by an amount (DSPL, e.g.,20 dB) that is due to Stapedius Reflex (e.g., when the user's voicetriggers a muscle response in the muscles supporting the bonestransmitting sound from the eardrum to cochlea), effectively dampingsome of the sound. Thus SPL_W(n)_(new)=SPL_W(n)−DSPL, whereSPL_W(n)_(new) is used in the Time_(—)100% (n) equation as opposed toSPL_W(n).

In this embodiment, rather than make use of the Sound Level (L), theperiod is a function of the loudness and quietness of the weighted soundpressure level. It should be noted that PSL (e.g., effective quiet) isused in the above example, but any level of interest, such as 80 dB, orno sound level, i.e., SPL_W(n)−0, can be used. The weighted soundpressure level and PSL can be expressed as a frequency-dependentnumerical array or a value scalar.

It is next determined whether or not the difference between the currentweighted sound pressure level and the PSL (e.g., effective quiet) isabove a tolerable threshold for risk of hearing damage or not, i.e.,whether the weighted SPL in the eardrum is considered to increase riskfor hearing damage or not. A sound pressure level dose is calculateddepending upon whether the sound level is loud or not. The soundpressure level dose (SPL Dose) is the measurement, which indicates anindividual's cumulative exposure to sound pressure levels over time. Itaccounts for exposure to direct inputs such as MP3 players, phones,radios and other acoustic electronic devices, as well as exposure toenvironmental or background noise, also referred to as ambient noise.The SPL Dose is expressed as a percentage of some maximum time-weightedaverage for sound pressure level exposure.

Because the sound pressure level dose is cumulative, there is no fixedtime-period for ear fatigue or damage. At or below effective quiet, thesound pressure level exposure time would theoretically be infinite,while the time period for achieving the maximum allowable sound pressurelevel dose becomes smaller and smaller with exposure to increasinglymore intense sound. A tolerable level change threshold corresponding tothe amount of noise above or below the effective quiet which has nogreat effect on the ear as compared to effective quiet is determined andstored in memory 127 in a step 320. In a step 322, the differentialbetween the weighted sound pressure level and the effective quiet iscompared to the level change threshold.

A differential value A, corresponding to the level change, can becalculated as follows:

A=SPL_(—) W(n)−PSL  (11)

If A is greater than the level change threshold, the noise is consideredto increase risk for hearing damage and the sound pressure level dose iscalculated in a step 324 as follows:

SPL Dose(n)=SPL Dose(n−1)+(Update_Epoch(n)/Time_(—)100%)  (12)

where SPL Dose(n−1) is the SPL Dose calculated during the last epoch;Update_Epoch is the time (in hours) since the last SPL Dose wascalculated. As described above, Update_Epoch can be adaptive, e.g.,shortened when the sound pressure level is louder; and Time_(—)100% (n),the time period remaining for safe exposure is determined by theequation:

Time_(—)100%(n)=24hours/(2̂((L−PSL)/3))  (13)

where L=sound level (in dB) of the combination of environmental noiseand audio playback. It should be noted that sound level (L) can besubstituted for SPL_W(n).

It should be noted, as can be seen from the equation, that the timevalue becomes more important than the sound pressure level as updatesare spread apart. However, this is to protect overexposure to harmfulsounds because a less accurate sample size must account for the unknown.The wider the periodicity, the less accurate determination of actualexposure. Infrequent updates of the SPL Dose assume a relativelyconstant sound level, ignoring transients (e.g. spikes) and interveningrestorative periods. Accordingly, sound pressure level and epochperiodicity are weighed against each other to protect the ear.

If in step 322 it is determined that the differential is not greaterthan the level change threshold, including negative values for A (whichare restorative values), then in step 326 it is determined whether ornot the differential, as determined in step 316, is less than the levelchange threshold in a step 322. If it is determined that thedifferential is not less than the level change threshold, then thereceived noise was the effective quiet level, i.e., the level changethreshold equals zero and in a step 330, the current SPL Dose ismaintained at the same level. There is no change to the dose level.However, if the differential A is less than the level change thresholdthen this is a restorative quiet as determined in step 326. Thus, if thedifferential A (e.g., A=SPL_W(n)−PSL) is less than zero, withinmeasurement error, then this is considered a restorative quiet, then then-th SPL dose is determined (at step 328) as

SPL Dose(n)=SPL Dose(n−1)*ê(−Update_epoch/τ)  (14)

Where: τ (referred to as “tau” in the following diagrams) can vary(e.g., equal to about 7 hours). In some exemplary embodiments, tau isadaptive for different users. In at least one exemplary embodiment, thelevel change threshold (e.g., measurement error) is set at substantially0.9-1.0 dB.

Note that other forms of a recovery function can be used and thedescription herein is not intended to limit the recover function to anexponential relationship. For example, during lower exposure times(e.g., 102 minutes) some SPL values (e.g., 95 dB) can be used, if thesubsequent SPL is less than PSL, in a linear manner (for examplelinearly decreasing until there is a near zero threshold shift at 4000Hz after one day from the time at which SPL<PSL).

Another non-limiting example of a recovery function can be a combinationover certain exposure and decay periods (e.g., 7 day exposure at 90 dB,with an initial threshold shift after the 7 days of about 50 dB at 4000Hz). For example a slow decaying linear relationship can be applied forthe first few hours (e.g., 2 hours) where SPL<PSL, then an exponentialdecay from after the first few hours to a few days (e.g., 4 days) afterwhich a leveling trend can occur.

Additionally although a fractional increase in SPL Dose is given as anon-limiting example, SPL Dose increase can be linear or exponentialdepending upon the exposure SPL level and the duration. For example thegrowth can be linear at a certain SPL values (e.g., 95 dB) duringdifferent ranges of exposure time (e.g., for 95 dB, from about 4 minutesto 12 hours), then leveling out (e.g., threshold shift of about 59.5 dB)when the exposure time exceeds a certain length (e.g., for 95 dB about12 hours).

In at least one exemplary embodiment the SPL values measured by an ECM(e.g., in an ECM mode) can be modified by a modification value (e.g.,additive or multiplicative), for example SPL_(new)=βSPL_(old)+8, wherethe values, β and δ, can be time variant, positive or negative.Alternatively the values can be applied to the measured pressure valuesin a similar manner. One can convert the SPL measured by an ECM to freefield values, which then can be compared to free field standards fordamage risk criteria. For example Table 1 lists several frequencydependent responses of an earpiece while inserted, the “A” weightingcurve offset, and the modification values β and δ.

TABLE 1 Earpiece “A” weight Freq. Resp. offset β δ Freq. (Hz) (dBSPL/V)(dB) (dB) (dB) 100 95 −19.1 1.0 0.00 500 103.5 −3.2 1.0 −0.13 1000 104.00.0 1.0 −1.83 2000 121.0 1.2 1.0 −7.84 4000 106.0 1.0 1.0 −15.57

Thus, for example an SPL (f) measured at 80 dB, at f=1000 Hz, would besubtracted by −1.83 to obtain a free field value to compare withdamage-risk criteria, thus obtaining an SPL_(new) of 78.13 dB. Note whatis described is a non-limiting example, various other earpieces can havedifferent values, and the SPL_DOSE equations, described herein, (e.g.,SPL_Dose(n), Time_(—)100%) can be based upon SPL_(new). Note thatfurther discussions concerning frequency responses and free fieldestimate (FFE) conversion can be viewed in U.S. Pat. No. 6,826,515,Bernardi et al. Alternatively ear canal dBA SPL (e.g., as measured by anECM) may be converted to FFE dBA SPL using Table 1 of ISO 11904-1(2002), incorporated herein by reference.

In step 332, the recovery time constant tau is determined. It may not bea function of exposure, but rather of recovery. It can be a defaultnumber or be determined as will be discussed below. As the SPL Dose iscalculated by system 100, it is also monitored. Once the SPL Dosereaches a certain level, as it is a cumulative calculation, ear fatiguecalculator 130 determines whether or not the SPL Dose corresponds to afatigued ear, and if so, it outputs warnings as discussed in connectionwith FIG. 1.

Reference is now made to FIG. 5 which depicts an optional methodologyfor not only updating the recovery time constant (tau) for individualusers, but to provide additional methods for acting upon detecteddamaging exposure. The process is started at a step 548. In a step 550,it is determined whether or not the user wishes to make use of aregistration process, for example online, for setting a personalizedupdate epoch through communication with a remote registration system. Ifthe user declines the registration, then the default tau is set at 7hours in a step 552. In a step 554, this default value is transmitted tosystem 100 via a wired or wireless data communication network.

Alternatively, if the user registers in step 550, a questionnaire ispresented in a step 556 in which the user informs system 100 regarding auser sound exposure history, age, work habits and other personal detailsthat could affect the user's personal recovery function time, i.e., thetime constant tau. The individual characteristics can be input to aformula or utilized as part of a look up table to determine the tau forthe individual user. The estimate of tau determined in step 556 istransmitted to system 100 via a wireless or wired data communicationsystem in a step 558. In step 560, the initial estimate of tau is setfrom the value determined in step 556 (or step 552).

An initial hearing test is performed in a step 561, which acquires dataindicative of the user's hearing sensitivity. The test may be anotoacoustic emission (OAE) test or audiogram administered utilizing theear canal receiver or speaker 25. However, the test can also beadministered over the Internet, telephone or other communication devicecapable of outputting sounds sent across a distributed network andenabling responsive communication. The data is stored in a computermemory as an initial test value in a step 570 and is used in furtherprocessing to detect a change in the user hearing response.

In a step 564, it is determined whether the user has been recentlyexposed to intense sound pressure levels. This can be done utilizing thesound pressure level dose as stored or permanently calculated by system100. If it is decided in step 564 that the user's ear canal soundpressure level is low, then in a step 559 it is determined whether thetime since the last test is greater than a maximum test epoch. At theoutset, the maximum test epoch is a set number determined in a step 562.In this non-limiting example, the maximum test epoch is set at 20 hours.

If it is determined that the time since the last test is greater thanthe maximum test epoch or, that there has been recent exposure tointense sound pressure level, then another test is administered in astep 566. The resulting test metrics are stored in steps 568, 570. In astep 571, the newly determined test metrics are compared to the initialtest metrics to calculate any change in the metrics. In step 572, it isdetermined whether the change is predictive of hearing damage. If not,then in a step 582, the tau is modified according the obtained metric.

If it is determined that the hearing damage is predicted, then in a step578 the user is recommended to remove themselves from the noise asdiscussed above with the operation of listening fatigue calculator 130and furthermore, the user can be recommended to seek professionalaudiological evaluation in a step 578. This could be done by an in situauditory or visual warning in step 580 by system 100. On the other hand,if system 100 is used in connection with a communications device such asa telephone or a personal digital assistant, an e-mail can be created insteps 574, 576; not only warning the user of potential damage, butnotifying a health professional so that a follow up examination can beperformed.

It should be noted that a change in the hearing metric (e.g., a hearingsensitivity curve) is measured by system 100. In response to the user'shearing metric, the recovery time constant tau is updated. For example,tau is lengthened if the change in the user's hearing metric indicatesthe user has “sensitive ears”, i.e., if, following loud sound exposure,the user's hearing sensitivity takes longer than seven hours to returnto the individual's normal. This modified tau can be used to calculatethe sound pressure level dose, in particular in a restorative phase, todetermine better overall effect of sound pressure level exposure.

By providing a monitoring and protective system which, in at least onemode, continuously monitors sound pressure level at the ear until apotentially harmful exposure has occurred, rather than only monitoringfor a predetermined time as with noise dose monitors which monitor forwork shifts, a more accurate predictor of harm to the ear is provided.By utilizing a method, which determines exposure in part as a functionof effective quiet exposure as well as intense noise exposure, anenhanced model of potential risk is achieved. By providing a series ofwarning mechanisms and preventive measures as a function of thedetermined potentially harmful dosage levels ear damage is more likelyto be prevented. By providing the system in an earpiece whichsubstantially occludes the ear and making use of audio inputs at thelateral and medial portions of the ear canal (particularly with anoccluding device between lateral and medial portions of the ear canal),a more accurate reading of noise level is provided and more controlthrough a real time warning system is achievable.

It should be known that values for level change threshold, effectivequiet time, and epoch were used above as examples. However, it should benoted that any values which when input and utilized in accordance withthe methodologies above prevent permanent damage to the ear are withinthe scope of the invention and the invention should not be so limited tothe specific examples above.

FURTHER EXEMPLARY EMBODIMENTS

FIG. 8 illustrates the general configuration and some terminology inaccordance with descriptions of exemplary embodiments. An earpiece 800can be inserted into an ear canal separating the ambient environment(AE) 890 from an inner ear canal (IEC) 880 region, where a portion ofthe earpiece 800 touches a part of the ear canal wall (ECW) 870. Theearpiece 800 can be designed to vary its distance from the eardrum (ED)860. The earpiece 800 can have various elements, and the non-limitingexample illustrated in FIG. 8, can include three sound producing orreceiving elements coupled to input/output 840: an ambient soundmicrophone (ASM) 830 configured to sample the AE 890; an ear canalmicrophone (ECM) 820 configured to sample the IEC 880; and an ear canalreceiver (ECR) 810 configured to acoustically emit into the IEC 880.

FIGS. 9A-9C illustrates an example of a temporal acoustic signal and itsconversion into a spectral acoustic signature. FIG. 9A illustrates atemporal acoustic signal (AS) 900 on a generic X-Y coordinate system(e.g., Y can be amplitude in dB, and X can be time in sec). A section910 of the AS 900 can be selected for further processing (e.g., forapplying filtering treatments such as a FFT). For the non-limitingexample of using a Fast Fourier Transform (FFT) on section 910, a window920 can be applied to the section 910 to zero the ends of the data,creating a windowed acoustic signal (WAS) 930. An FFT can then beapplied 940 to the WAS 930 to generate a spectral acoustic signal (SAS)950, which is illustrated in FIG. 9C, where the Y-axis is a parameter(e.g., normalized power) and the X-axis is frequency (e.g., in Hz).

FIG. 10 illustrates a generalized version of an earpiece 800 and someassociated parts (e.g., ASM 830, ECM 820, and ECR 810) in an ear canal.When inserted the earpiece 800 generally defines the two regions 890 and880. Through the earpiece 800 there is some attenuation. For example anambient acoustic signal (AAS) 1010A, will travel through the earpiece800 and/or via bone conduction (not shown) and be attenuated forming anattenuated ambient acoustic signal (AAAS) 1010B. The AAAS 1010B thentravels to the ED 860. The other additional acoustic signal 1010C (e.g.,the ECR generated AS or ECRAS), which can travel to the eardrum 860, canbe generated by the ECR 810. Thus the total AS imparting energy upon theED 860 can be due to the AAAS 1010B (which can include a bone conductionpart not in the IEC 880) and the ECRAS 1010C. Various exemplaryembodiments can calculate SPL Dose due to the total imparting AS uponthe ED860, using various combinations of elements (e.g., parts) such asthe ECR 810 (e.g., Knowles FG3629), the ECM 820 (e.g., Knowles FK3451),and the ASM 830 (e.g., Knowles FG3629). Note that ECM 820 can alsomeasure head attenuated acoustic signals (HAAS) 1010D, which for examplecould originate from voice.

FIG. 11 illustrates an earpiece 1100 according to at least one exemplaryembodiment including an ECR 810 and an ECM 820 (not shown). ECRAS 1010Cgenerated by the ECR 810 can be predicted and used to predict anequivalent SPL Dose as discussed later. Note that additional elements(e.g., logic circuit(s) (LC), power source(s) (PS), can additionally beincluded in the earpiece 1100). For example FIG. 12 illustrates a selfcontained version of an earpiece 1200 according to at least oneexemplary embodiment, including a power source (PS) 1210 (e.g., zinc-airbattery (ZeniPower A675P), Li-ion battery), and a logic circuit (LC,e.g., Gennum Chip GA3280) 1220 in addition to ECR 810. Earpiece 1200 canalso include a wireless module for wireless communications (not shown)or can be wired. Earpiece 1200 can also connect remotely to variousparts (e.g., via a wired or wireless connection). For example FIG. 13illustrates an earpiece 1300 where parts are not contained in theearpiece directly according to at least one exemplary embodiment. Asillustrated the LC 1220 and PS 1210 are operatively connected (OC) 1310(e.g., via a wire or wirelessly) to the earpiece 1300. For exampleearpiece 1300 can be an earbud that includes ECR 810, whose signalstravel back and forth via a wire that is operatively connected via awire to LC 1220, which in turn can be operatively connected to PS 1210.Note that ECR 810 can also be a dual purpose ECR/ECM, where when thereceiver function (ECR mode) is not used the microphone function (ECMmode) can be used. For example U.S. Pat. No. 3,987,245 discusses a dualpurpose transducer that can be used as a microphone and/or a receiver.

FIG. 14A illustrates a general configuration of some elements either inor connected to an earpiece 1400 (e.g., via a wired or wirelessconnection) according to at least one exemplary embodiment. Illustratedis a logic circuit LC 1220 that is operatively connected 1310B to areadable memory 1420. LC 1220 can store and read data on the readablememory 1420 (e.g., RAM). LC 1220 can also be operatively connected 1310Cto ECR 810, such that acoustic signals can be received by LC 1220 fromECR 810 and signals sent from LC 1220 to ECR 810, where ECR 810 isconfigured to direct acoustic energy toward the eardrum. LC 1220 canalso be operatively connected 1310E (e.g., via wire or wireless) to acommunication module 1410 (e.g., Bluetooth communication module). Topower the various elements a power source 1210 PS can also beoperatively connected 1310F to LC 1220 and to any other element.

FIG. 14B illustrates a flow diagram of a method for SPL Dose calculationaccording to at least one exemplary embodiment. A signal (e.g., intendedaudio playback content, or received voice from a phone) can be sent toLC 1220 to be sent to the ECR 810. The signal can be converted (e.g.,using earpiece frequency response) to calculate the SPL(t) associatedwith the signal being sent to ECR 810. Thus the signal to the ECR 810can be measured in step 1450A, an SPL measured for a chosen period oftime. An SPL_Dose estimate is calculated as described above, in a step1450B. The SPL_Dose estimate is added/subtracted to/from a running SPLDose total to obtain a new SPL Dose total in a step 1450C. The new SPLDose total is compared to a threshold value in a step 1450D. If thethreshold value is exceeded the LC 1220 compares a check actionparameter, which can be a user defined variable, to determine one ormore actions to take in a step 1450E. For example if the actionparameter is a certain value (e.g., 1) then the action can be to modifydevice operation in a step 1450H. For example, to shut down the deviceafter a period of time (e.g., 5 seconds). Alternatively or cumulatively,if the action parameter is another value (e.g., 2), a notificationsignal can be sent (e.g., acoustic notice, for example a ringing) in astep 1450F, and/or if the action parameter is still another value (e.g.,3) the audio content can be modified (e.g., SPL output by ECR sreduced), in a step 1450G. Note other actions can be included, in a step14501, for example the NRR can be increased (e.g., if an inflatablesystem, the inflatable system can be expanded, or active noisecancellation could be activated).

Note that at least one exemplary embodiment can use an ECR 810 withoutdual functionality (e.g., where dual functionality is an ECR that can bea receiver and/or a microphone) and at least one further exemplaryembodiment can be a dual function ECR/ECM. To measure the SPL for an ECRonly mode (ECR mode) the same SPL Dose equations described above can beused for the SPL estimated as discussed with reference to FIG. 14B.Additionally the SPL_(ECR) can be estimated by an ECR instrumentresponse, e.g., a voltage to FFE dBA transfer function, which could bedetermined one of two ways: apply voltage to ECR 810 and follow thetechnique outlined in ISO 11904-2 (2002), using an acoustic manikinand/or apply voltage to ECR 810 and follow the technique outlined in ISO11904-1 (2002), using probe microphone measurements in a human's earcanal; and/or about a 2 cc coupler could substitute for a human's earcanal.

FIG. 14C illustrates a flow diagram of a method of SPL Dose calculationaccording to at least one exemplary embodiment. In addition to anexemplary embodiment where only an ECR 810 is operating, a dual ECR/ECMcan be used. Thus ECR 810 can be switched in such a case between an ECRmode, where audio signal is directed to the ECR 810 (e.g., audioplayback (e.g., music, audio book, voice message), or voice conversation(e.g., voice from a phone, TV, computer)) or to an ECM mode, where ECR810 acts as an ECM and samples environmental SPL. FIG. 14C illustrates amethod in accordance with at least one exemplary embodiment and firstcomprises: determining which mode ECR 810 is in, ECR mode or ECM mode,in step 1470A. If ECR 810 is in the ECR mode the method as discussedwith reference to FIG. 14B, in step 1470B, can be used to obtain anSPL_(ECR) estimate, within the sample time “t” in a step 1470B, toeither obtain SPL_Dose_(ECR) in a step 1470C, or save the value ofSPL_(ECR) to be added later to an SPL value for the environment, withinsample time “t”, to obtain a total SPL and then calculate a total SPLDose in a step 1470D. Because in the ECR mode an ECM measurement is notmade, the true environmental SPL value is not obtained, however severalmethods can be used to obtain a predicted sound pressure level (PSPL)for the environment during the ECR mode. One of these methods, otherswill be discussed with respect to FIGS. 15E and 17A, is to use the lastSPL_(ECM) value recorded, throughout the sample time “t” to obtain anSPL_Dose_(ECM) then add SPL_Dose_(ECR) to SPL_Dose_(ECM) to get SPLDose_(total). Alternatively, one can obtainSPL_(total)=SPL_(ECR)+SPL_(ECM), then calculate SPL Dose_(total) whereSPL_(total) can be used in “A” to determine if a recovery function isused for calculation of SPL Dose_(total).

Additionally, ECM mode data can be saved as a function of day of theweek and time of day, and used to correct any PSPL estimated that mayoccur at the same time and day in the future, which would correct anySPL_Dose_(ECM) obtained using PSPL in a step 1470E, and a new SPLDose_(total) can be calculated in a step 1470F. The new SPL Dose totalcan be compared to a threshold value in a step 1470K, and if thethreshold value is exceeded the LC 1220 compares a check actionparameter, which can be a user defined variable, to determine one ormore actions to take in a step 1470L. For example if the actionparameter is a certain value (e.g., A) then the action can be to modifydevice operation in a step 1470M, for example to shut down the deviceafter a period of time (e.g., 10 seconds). Alternatively orcumulatively, if the action parameter is another value (e.g., B), anotification signal can be sent (e.g., acoustic notice, for example anotification voice recording) in a step 1470P, and/or if the actionparameter is still another value (e.g., C) the audio content can bemodified (e.g., SPL output by ECR can be reduced) in a step 14700. Noteother actions can be included in a step 1470N, for example the ECRemitted intensity can be reduced.

If ECR 810 is placed into ECM mode, then SPL_(ECM) can be measured inECM mode in a step 1470G, and an ambient SPL Dose_(ECM) calculatedduring the sampling time “t1” in a step 1470H. Note the SPL Dose_(ECM)calculated can be stored for future reference in a step 14701 and/orSPL_(ECM) can be stored as a function of prediction variables (e.g.,time of day, day of the week) in a step 1470J.

FIG. 14D illustrates a flow diagram of a method of SPL Dose calculationaccording to at least one exemplary embodiment. The method includes:calculating the SPL_Dose during the ECR mode for time increment “Δt” ina step 1480A. PSPL for the same time increment is calculated in a step1480B. This can include using SPL data from ECM mode measurements savedin a database 1492. SPL_Dose for the ECM mode is calculated during thesame time increment using PSPL. SPL_Dose total is calculated in a step1480C. Note that SPL for the ECR mode and PSPL can be combined formingan SPL total and then SPL_Dose total is calculated in a step 1480D.SPL_Dose total is compared to a threshold value, for example thethreshold value can be equivalent to a % of the remaining allowableSPL_Dose during the day (e.g. SPL_Dose is 90% allowable but with only 5%of the day remaining) in a step 1480E, and if the threshold value isexceeded the LC 1220 compares a check action parameter, which can be auser defined variable, to determine one or more actions to take in astep 1480F. For example if the action parameter is a certain value(e.g., MOD) then the action can be to modify device operation in a step1480J, for example to shut down any ECR generated audio content.Alternatively or cumulatively, if the action parameter is another value(e.g., NOTF), a notification signal can be sent (e.g., acoustic notice,for example an acoustic earcon) in a step 1480G, and/or if the actionparameter is still another value (e.g., AUDCON) the audio content can bemodified (e.g., SPL output by ECR can be reduced) in a step 1480H. Noteother actions can be included in an omnibus step 14801, for example theECR emitted intensity can be reduced.

FIGS. 15A-15E illustrate a method of switching between ECR and ECM modesin accordance with at least one exemplary embodiment. FIG. 15Aillustrates a plot of SPL_(ECR) versus time. At certain times, e.g. t1,SPL_(ECR) falls below a selected floor (SF), e.g., threshold hearing SPLlevel at 1000 Hz, which could last to a time of t1+Δt1. During this timeperiod a dual ECM/ECR mode capable ECR 810 could then monitor ambientSPL levels in an ECM mode. Thus in at least one exemplary embodimentwhen the SPL in the ECR mode drops below the SF a trigger signal (e.g.,sts_(ECM)) can be sent to LC 1220 to switch to ECM mode for measuringambient SPL (FIG. 15B). There can be a delay, t_(delay), between whenthe SPL in the ECR mode drops below SF and when the signal sts_(ECM), isreceived by LC 1220. Upon receiving sts_(ECM) the dual ECR/ECM modecapacity ECR 810 can start monitoring SPL_(ECM), FIG. 15D.

Thus there will be sections of time throughout the day where SPL_(ECM)is measured (e.g., t1 to t1+Δt1, t2 to t2+Δt2, t3 to t3+Δt3, and t4 tot4+Δt4), these values can be saved and used later to fit a function ofPredicted SPL (PSPL) for the particular day (e.g., PSPL₂₄=A+Bt+Ct̂2+Dt̂3,using a least squares fit to the measured data for that day to obtaincoefficients A, B, C, D). In at least one exemplary embodiment PSPL₂₄can be used at the end of the day to refine (e.g., replace, averagewith) the PSPL used during that day to update the SPL_Dose equation.Note that PSPL₂₄ can be saved in a database (i.e., the coefficients A,B, C, D) as a function of various variables (e.g., day of the week,holiday period, seasons) and refined (e.g., updated with more data) overtime. Thus, in at least one exemplary embodiment, PSPL₂₄ for that daycan be used to refine predicted SPL_(ECM) (PSPL) during ECR mode, whilethe actual data SPL_(ECM) is used when measured (e.g., FIG. 15E). Notesince drive signals (e.g., audio playback signals, voice communicationsignals, alarm signals) sent (sometimes referred to herein as acousticsignals sent) to ECR 810 are known, then it will be known when to send asignal sts_(ECR) to LC 1220 to switch back to ECR mode (FIG. 15C). Thusthe total ambient SPL (FIG. 15E) before update with PSPL₂₄, will be acombination of calculated PSPL during ECR mode operations and actualmeasurements SPL_(ECM).

There are multiple methods of calculating PSPL, and we will discuss fivenon-limiting examples in detail.

First Example of Calculating PSPL

The first non-limiting example for calculating PSPL uses averages of thepreceding and following SPL_(ECM) values with respect to the PSPL beingpredicted. Thus, with reference to FIGS. 15D and 15E, PSPL_(ECM1)(t) canbe estimated as:

$\begin{matrix}{{{PSPL}_{{ECM}\; 1}( {( {t_{1} + {\Delta \; t_{1}}} ) < t < t_{2}} )} = \frac{\lbrack {\begin{matrix}( {\frac{1}{\Delta \; t_{1}}{\int_{t_{1}}^{t_{1} + {\Delta \; t_{1}}}{{{SPL}_{{ECM}\; 1}(t)}\ {t}}}} ) \\( {\frac{1}{\Delta \; t_{2}}{\int_{t_{2}}^{t_{2} + {\Delta \; t_{2}}}{{{SPL}_{{ECM}\; 2}(t)}\ {t}}}} )\end{matrix} +} \rbrack}{2.0}} & (15)\end{matrix}$

Thus, FIG. 15E illustrates PSPL estimates as straight lines (although ofcourse other methods and techniques can be used that will not result instraight lines). These estimated PSPL can be later refined by use ofPSPL_(tupdate), where PSPL_(tupdate), is an equation refined by the dataover the tupdate period (e.g., PSPL₂₄, where tupdate is 24 hours in thenon-limiting example previously discussed, note tupdate can be anyperiod of time with enough data to solve the coefficients of theparticular form of the equation). Note that the integrals can bereplaced with summations, for example when manipulating digitized data.

Second Example of Calculating PSPL

A second non-limiting example of calculating PSPL uses weightedaverages, where the SPL_(ECM) data can be weighted according to severalfactors, for example the time increment during which measurements aremade. A time incremented weighting can be expressed as:

$\begin{matrix}{{{PSPL}_{{ECM}\; 1}( {( {t_{1} + {\Delta \; t_{1}}} ) < t < t_{2}} )} = \frac{\begin{bmatrix}{{\frac{\Delta \; t_{1}}{{\Delta \; t_{1}} + {\Delta \; t_{2}}}( {\frac{1}{\Delta \; t_{1}}{\int_{t_{1}}^{t_{1} + {\Delta \; t_{1}}}{{{SPL}_{{ECM}\; 1}(t)}\ {t}}}} )} +} \\{\frac{\Delta \; t_{1}}{{\Delta \; t_{1}} + {\Delta \; t_{2}}}( {\frac{1}{\Delta \; t_{2}}{\int_{t_{2}}^{t_{2} + {\Delta \; t_{2}}}{{{SPL}_{{ECM}\; 2}(t)}\ {t}}}} )}\end{bmatrix}}{2.0}} & (16)\end{matrix}$

Third Example Of Calculating PSPL

A third non-limiting example is a linear model of the PSPL in time. Forexample, where in general PSPL is expressed as PSPL(t)=X+Yt. Usingaverage values an example of a linear model can be expressed as:

$\begin{matrix}{{{PSPL}_{{ECM}\; 1}(t)} = {{\frac{1}{\Delta \; t_{1}}{\int_{t_{1}}^{t_{1} + {\Delta \; t_{1}}}{{{SPL}_{{ECM}\; 1}(t)}\ {t}}}} + {{\eta_{{({t_{1} + {\Delta \; t_{1}}})}arrow t_{2}}(t)}t}}} & (17)\end{matrix}$

Where in this non-limiting example X is the average of the precedingSPL_(ECM) values, and Y is η=constant, where η can be expressed as:

$\begin{matrix}{{\eta_{{({t_{1} + {\Delta \; t_{1}}})}arrow t_{2}}(t)} = {{{const}.} = {\frac{1}{t_{2} - ( {t_{1} + {\Delta \; t_{1}}} )}\begin{bmatrix}{{\frac{1}{\Delta \; t_{2}}( {\int_{t_{2}}^{t_{2} + {\Delta \; t_{2}}}{{{SPL}_{{ECM}\; 2}(t)}\ {t}}} )} -} \\{\frac{1}{\Delta \; t_{1}}( {\int_{t_{1}}^{t_{1} + {\Delta \; t_{1}}}{{{SPL}_{{ECM}\; 1}(t)}\ {t}}} )}\end{bmatrix}}}} & (18)\end{matrix}$

Fourth Example of Calculating PSPL

A fourth non-limiting example is a linear model of the PSPL in time. Forexample, where in general PSPL is expressed as PSPL(t)=X+Yt. Usingpreceding and trailing last values of SPL_(ECM), where an example of alinear model can be expressed as:

PSPL_(ECM1)(t)=SPL_(ECM1)(t ₁ +Δt ₁)+η_((t) ₁ _(+Δt) ₁ _()→t) ₂(t)t  (19)

Where in this non-limiting example X is the last of the precedingSPL_(ECM) values, and Y is η(t), where η can be expressed as:

$\begin{matrix}{{\eta_{{({t_{1} + {\Delta \; t_{1}}})}arrow t_{2}}(t)} = {\frac{1}{t_{2} - ( {t_{1} + {\Delta \; t_{1}}} )}\lbrack {{{SPL}_{{ECM}\; 2}( t_{2} )} - {{SPL}_{{ECM}\; 1}( {t_{1} + {\Delta \; t_{1}}} )}} \rbrack}} & (20)\end{matrix}$

Fifth Example of Calculating PSPL

A fifth non-limiting example examines a non-linear model of PSPL intime. For example, where in general PSPL is expressed asPSPL(t)=α+βt+δt²+ . . . . In one method the actual values in thepreceding and trailing sections of SPL_(ECM) can be compared to themodel PSPL results upon parameter (e.g., α, β, δ) choices in a leastsquares approach. Note in this case PSPL is modeled from t₁ to t₂+Δt₂.For example a model of PSPL can be solved via the expression:

$\begin{matrix}{ {{PSPL}_{{ECM}\; 1}(t)}\Rightarrow\alpha , \beta, {\delta \overset{minimize}{arrow}{\quad{\quad\begin{pmatrix}{{\int_{t_{1}}^{t_{1} + {\Delta \; t_{1}}}{\lbrack {{{PSPL}_{i}(t)} - {{SPL}_{{ECM}\; 1}(t)}} \rbrack^{2}{t}}} +} \\{\int_{t_{2}}^{t_{2} + {\Delta \; t_{2}}}{\lbrack {{{PSPL}_{i}(t)} - {{SPL}_{{ECM}\; 2}(t)}} \rbrack^{2}{t}}}\end{pmatrix}}}}} & (21)\end{matrix}$

Note to minimize one can take the derivative of the above equation andlook for the inflection points as a function of i. Note in the aboveequation PSPL_(i) can be expressed as:

PSPL_(i)(t)=α_(i)+β_(i) t+δ _(i) t ²+  (22)

where a value for PSPL_(i) is obtained for “t” by selecting a guess(“ith” guess) for the parameters, then incrementing (“i+1”) theparameters to get a new value for PSPL_(i+1), the procedure of which isknown by one of ordinary skill in the relevant arts.

Note that the above five examples of calculating PSPL are non-limitingexamples and other methods can be used.

FIGS. 16A-16C illustrate the formation of SPL total from ECM and ECRvalues and estimated values (PSPL). For example FIG. 16A illustrates twoSPL values in the interval 0 to t₁, SPL_(ECR0)(t) and PSPL_(ECM0)(t).Both of these values can be added to form SPL_(total)(t) in the sameinterval from 0 to t₁ (FIG. 16B). As discussed the value of SPL_(total)can be compared with PSL to determine whether one is in a SPL_Dosegrowth phase (SPL_(total)>PSL) or a recovery stage (SPL_(total)<PSL)(FIG. 16C). Note that the jumps in SPL_(total) can result when no signalis sent to ECR 810 to emit acoustic energy to the eardrum. When SPLtotal is above PSL, SPL_Dose increases. Over the period of the day,SPL_Dose will increase or decrease. At least one exemplary embodimentadjusts the SPL_Dose after an update period (e.g., 24 hours). Forexample the data from actual measurements of SPL_(ECM)(t) (e.g., duringt₁ to t₁+Δt₁, during t₂ to t₂+Δt₂, during t₃ to t₃Δt₃, and during t₄ tot₄+Δt₄) can be used to obtain a PSPL_(update), for example using amethod similar to the fifth PSPL calculating example discussed above.The values provided by the equation PSPL_(update) (t) can be used inplace of PSPL_(ECM0)(t), PSPL_(ECM1)(t), etc. . . . and the new valuesused to update SPL_Dose total. In at least one further exemplaryembodiment, instead of replacing PSPL_(ECM0)(t), PSPL_(ECM1)(t), etc. .. . , the relevant values of PSPL_(update) (t) can be combined (e.g.,weighted average). For example FIGS. 17A-17C illustrate replacement ofPSPL_(ECM0)(t), PSPL_(ECM1)(t), . . . values with relevant PSPL_(day)(t)values, where the update time is 24 hours or a day. Thus FIG. 17Aillustrates the estimated SPL_(ECR)(t) values along with relevantPSPL_(day)(t) values. Note that the actual measured values ofSPL_(ECM)(t) can be used instead of the PSPL_(day)(t) values in the timeincrement (e.g., from t₁ to t₁Δt_(t)). The final SPL_(total-adjusted)(t)values can be obtained by combining SPL_(ECR)(t) values along withrelevant PSPL_(day)(t) values, FIG. 17B, where SPL_(total-adjusted)(t)can have different values than SPL_(total-adjusted)(t)=SPL_(total)(t)(FIG. 16C) as illustrated in FIG. 17C. As mentioned previously whenSPL_(total)>PSL, SPL_Dose is in a growth stage, and whenSPL_(total)<PSL, SPL_Dose is in a recovery stage, as illustrated in FIG.17D.

Exemplary embodiments of the present invention can be used in manyplatforms that direct and/or attenuate acoustic energy in the ear canal.FIGS. 18A to 18N illustrate various non-limiting examples of earpiecesthat can use methods according to at least one exemplary embodiment,when the various earpieces have an ECR 810 that is solely an ECR or havean ECR 810 that has dual ECR/ECM modes.

FIG. 19 illustrates a line diagram of an earpiece 1900 (e.g., havingearbud 1910) that can use methods according to at least one exemplaryembodiment and FIG. 20 illustrates the earpiece of FIG. 19 fitted in anear canal. Earbuds 1910 can be used with many devices such as audioplayback devices, PDAs, phones, and other acoustic management devices.The software to implement exemplary embodiments can reside in theearpiece (e.g., hearing aid) or can reside in the acoustic managementsystems (e.g., iPod™, Blackberry™, and other acoustic management devicesas known by one of ordinary skill in the relevant arts).

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions of therelevant exemplary embodiments. For example, although specific numbersmay be quoted in the claims, it is intended that a number close to theone stated is also within the intended scope, i.e., any stated number(e.g., 80 dB) should be interpreted to be “about” the value of thestated number (e.g., about 80 dB). Thus, the description of theinvention is merely exemplary in nature and, thus, variations that donot depart from the gist of the invention are intended to be within thescope of the exemplary embodiments of the present invention. Suchvariations are not to be regarded as a departure from the spirit andscope of the present invention.

1. A method of operating an audio device comprising: calculatingestimated sound pressure levels (SPL1) for drive signals directed to anear canal receiver (ECR) during a time increment Δt, when the ECR is inan ECR mode; measuring sound pressure levels (SPL2) for ambient acousticsignals received by the ECR during the time increment Δt, when the ECRis in an ear canal microphone (ECM) mode; calculating an estimatedSPL_Dose during the time increment Δt using at least one of SPL1 andSPL2; and calculating a total SPL_Dose of the audio device at a time tusing the estimated SPL_Dose.
 2. The method according to claim 1,further including: comparing either sound pressure levels SPL1 or SPL2to a permissible sound level (PSL), and if the used sound pressurelevels, SPL1 or SPL2, is less than PSL within an error margin, then thestep of calculating an estimated SPL_Dose uses a recovery function tocalculate the estimated SPL_Dose during the time increment Δt.
 3. Themethod according to claim 2, where the error margin is zero.
 4. Themethod according to claim 1, further comprising: comparing the totalSPL_Dose to a threshold value and if the total SPL_Dose is greater thanthe threshold value then an action parameter is read from readablememory.
 5. The method according to claim 4 further comprising:performing an action associated with the action parameter, where theaction is at least one of modifying the operation of the audio device,modifying the drive signals directed to the ECR, and sending an acousticnotification signal to a user.
 6. A method of operating an audio devicehaving an ear canal receiver (ECR) capable of operating in an ECR or earcanal microphone (ECM) mode comprising: calculating estimated soundpressure levels (SPL1) for drive signals directed to the ECR during atime increment Δt, when the ECR is in the ECR mode; predicting a soundpressure level (PSPL1) for ambient acoustic signals that would bereceived by the ECR during the time increment Δt, if the ECR was in theECM mode but is in ECR mode; calculating an estimated SPL_Dose duringthe time increment Δt as a function of SPL1 and PSPL1; and calculating atotal SPL_Dose of the audio device at a time t using the estimatedSPL_Dose.
 7. The method according to claim 6, further comprising:measuring sound pressure levels (SPL2) for ambient acoustic signalsreceived by the ECR during the time increment Δt, when the ECR is in theECM mode.
 8. The method according to claim 7, further including:calculating an SPL total during the time increment Δt using SPL1 andPSPL1, when the ECR is in the ECR mode.
 9. The method according to claim8, where if the ECR is in the ECM mode during the time increment Δt,then SPL total during the time increment Δt is calculated using SPL2.10. The method according to claim 9, further comprising: comparing theSPL total to a permissible sound level (PSL), and if SPL total is lessthan PSL within an error margin, then the step of calculating anestimated SPL_Dose uses a recovery function to calculate the estimatedSPL_Dose during the time increment Δt.
 11. The method according to claim10, where the error margin is zero.
 12. The method according to claim 7,further comprising: generating a PSPL(t) equation valid over an updatetime period using at least two measured SPL2 values within an updatetime period.
 13. The method according to claim 12, where the values fromthe PSPL(t) equation during the time increment Δt are used in place ofPSPL1 in calculating SPL total.
 14. The method according to claim 10,further comprising: comparing the total SPL_Dose to a threshold valueand if the total SPL_Dose is greater than the threshold value then anaction parameter is read from readable memory.
 15. The method accordingto claim 14 further comprising: performing an action associated with theaction parameter, where the action is at least one of modifying theoperation of the audio device, modifying the drive signals directed tothe ECR, and sending an acoustic notification signal to a user.
 16. Amethod of operating an audio device comprising: calculating estimatedsound pressure levels for drive signals directed to an ear canalreceiver (ECR) during a time increment Δt; calculating an estimatedSPL_Dose during the time increment Δt using the estimated sound pressurelevels; comparing the estimated sound pressure levels to a permissiblesound level (PSL), and if the estimated sound pressure levels are lessthan PSL then the step of calculating an estimated SPL_Dose uses arecovery function that is at least one of a linear function and anexponential function to calculate the estimated SPL_Dose during the timeincrement Δt; and calculating a total SPL_Dose at the time t of theaudio device using the estimated SPL_Dose, where t=t₀+Δt, where t₀ isthe time at the beginning of the time increment Δt.
 17. A method ofoperating an audio device comprising: calculating estimated soundpressure levels (SPL1) for drive signals directed to an ear canalreceiver (ECR) during a time increment Δt, when the ECR is in an ECRmode; measuring sound pressure levels (SPL2) for ambient acousticsignals received by the ECR during the time increment Δt, when the ECRis in the ear canal microphone (ECM) mode; predicting a sound pressurelevel (PSPL1) for ambient acoustic signals that would be received by theECR during the time increment Δt, if the ECR was in the ECM mode but isin the ECR mode; calculating an SPL total during the time increment Δtusing SPL1 and PSPL1 when the ECR is in the ECR mode, if the ECR is inthe ECM mode during the time increment Δt then SPL total during the timeincrement Δt is calculated using SPL2; calculating an estimated SPL_Doseduring the time increment Δt using SPL1 and PSPL1 when the ECR is in ECRmode and SPL2 when ECR is in ECM mode; comparing the SPL total to apermissible sound level (PSL), and if SPL total is less than PSL thenthe step of calculating an estimated SPL_Dose uses a recovery functionthat is at least one of a linear function and an exponential function tocalculate the estimated SPL_Dose during the time increment Δt; andcalculating a total SPL_Dose of the audio device at a time t using theestimated SPL_Dose, where t=t₀+Δt, where t₀ is the time at the beginningof the time increment Δt.
 18. The method according to claim 17, wherethe step of predicting a sound pressure level (PSPL1) for ambientacoustic signals uses at least one preceding SPL2 value before t₀, andat least one trailing value of SPL2 after t.
 19. The method according toclaim 18, where the value(s) of PSPL1 is calculated by one of thefollowing, a constant based on an average value of the preceding SPL2value and the trailing SPL2 value, a linear function in time based onthe preceding SPL2 value and the trailing SPL2 value, and a nonlinearfunction in time based on the preceding SPL2 value and the trailing SPL2value.
 20. An earpiece comprising: an ear insertable housing; and an earcanal receiver, where the ear canal receiver is at least partially inthe housing, and where the ear canal receiver can be switched between anear canal receiver mode and an ear canal microphone mode.